1. Field of the Invention
This invention relates to bone conduction-speakers, in general, and to a bone-conduction speaker-unit particularly employable for earbud speakers.
2. Description of the Related Art
As is known, bone-conduction speakers function on a principle where the speaker typically includes a transducer to receive an electrical signal (such as an audio signal) and to generate a controlled vibration in response. When worn, the transducer transmits the vibration to the bones of the wearer's skull—from which, it is transmitted to the wearer's inner ear. The bone conduction then enables sound to be transmitted this way to the wearer's inner ear by vibration, rather than by way of sound waves that travel through the air to enter the wearer's outer ear.
Bone-conduction speaker designs, however, typically suffer from somewhat less than optimal sound richness quality, particularly at the low and mid frequency ranges; they also tend to exhibit noticeable amounts of decreased durability in use. Experience has shown these undesirable features become more pronounced, furthermore, as the wearer ambulates in tending to move about, instead of his/her just sitting in place. Testings have shown that this is at least partially because of the manners by which the innards of the bone-conduction speaker have been stabilized—most often with bonding adhesive techniques.